The problem of the oil mill wastewaters is well known. The olives pressing in the oil productive countries creates as by-product, at the rate of 40/50% of the weight of the pressed olives, oil mill wastewaters rich in highly polluting organic compounds (polyphenols) which create a number of environment and ecological problems connected with their elimination and treatment.
Many methods have been proposed to eliminate this kind of problem, for example by a technique of photo catalysis, ozonization, etc., but up to today no satisfying solution is available yet, in particular a solution which does not involve a drastic contraction of production with a strong increase of prices.
On the other hand, it is known that the oil mill wastewaters contains metabolites of interest for the cosmetic, pharmaceutical, dietetic and food industry. The isolation of these metabolites, especially Tyrosol and Hydroxytyrosol, from the oil mill wastewaters, is therefore an aim of particular applied interest, thanks to their antioxidant properties.
For example, WO2004/005228 describes an extraction process of Hydroxytyrosol, comprising the acidification of the oil mill wastewaters followed by extractions by organic solvents and supercritical fluids.